A biomechanical hypothesis for the pathophysiology of apical lung disease

ObjectiveA hypothesis is presented suggesting that the pathogenesis of apical lung disease is due to progression of subclinical congenital apical bullae in people with low Body Mass Index (BMI), a combination present in 15% of the population, due to high pleural stress levels present in the antero-posteriorly flattened chests of these individuals.DesignThe hypothesis was tested for validity in two apical lung pathologies with widespread epidemiological literature, namely tuberculosis (TB) and primary spontaneous pneumothorax (PSP), assessing whether the hypothesis could identify high-risk populations, explain exceptional cases like apical lower lobe disease and confirm predictions.ResultsThe biomechanical hypothesis can explain the high-risk factors of apical location, age, gender and low-BMI build, as well as the occurrence of disease in the apex of the lower lobe, in both TB and PSP patients. A predicted common pathogenesis for apical lung disease was confirmed by the higher-than-expected incidence of concomitant TB and PSP.ConclusionPleural stress levels depend on chest wall shape, but are highest in the apex of young males with low BMI, leading to growth of congenital bullae that can eventually limit clearance inhaled material, superinfect or burst. This hypothesis suggests that low-dose computerized tomography may be used to screen for TB eradication. This paper is the first to propose a biomechanical mechanism for all apical lung disease pathophysiology.